Process for producing vinyl polymers

ABSTRACT

The present invention provides a process for producing a vinyl polymer characterized in that, in a radical polymerization of a vinyl monomer, a substituted hydroxylamine represented by a general formula:  
                 
 
     (in which R 1  and R 2  represent hydrogen, a (substituted) aliphatic hydrocarbon group having one or more carbon atom(s) or an aromatic hydrocarbon group) and/or a general formula:  
                 
 
     (in which; and R 3  and R 4  represented a (substituted) aliphatic hydrocarbon group having one or more carbon atom(s)) is added.  
     A radically polymerized vinyl polymer having a high molecular weight and a restrained molecular weight distribution can be obtained by the process of the present invention, even under a polymerization condition at a high temperature. The present invention provides, therefore, a process enabling to produce vinyl polymers which promise to have practical properties such as appearance, mechanical properties and heat resistance useful as materials for various moldings and coatings. Thus, the industrial and practical value of the present invention is extremely high.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method of radicalpolymerization of a vinyl monomer in the presence of a specificsubstance, and particularly, to a process for efficiently producing avinyl polymer which has a high molecular weight desirable for practicalproperties such as mechanical properties, heat resistance and the like,and which has controlled molecular weight distribution.

[0003] 2. Description of the Prior Art

[0004] In conventional radical polymerization, the molecular weight ofthe produced polymer strongly depends on the polymerization temperature,that is, the molecular weight of the polymer obtained is restricted bythe polymerization temperature. Although the polymerization temperatureis typically lowered in order to achieve a high molecular weight,decrease in polymerization temperature will elongate the polymerizationtime and increase the amount of remaining monomer. It becomes,therefore, difficult to effect an efficient production. Similarly,although the polymerization temperature is typically elevated in orderto achieve a low molecular weight, increase in polymerizationtemperature so accelerate the polymerization rate that it becomesdifficult to control the reaction. For these reasons, there is a wideneed for a polymerization method of freely onto the molecular weight ina radical polymerization.

[0005] As an attempt to control the molecular weight in a radicalpolymerization, Tatemoto et al. have reported that radicalpolymerization of a fluorine-containing monomer such astetrafluoroethylene proceeds in a manner like living polymerization inthe presence of an iodine compound such as (CF₃)₂CF-I (Sozo Tatemoto,Koubunshi-Ronbun-Shu 49, 765 (1992)). Likewise, Otsu et al. have foundthat, when certain sulfur compounds were used, radical polymerization ofstyrene or the like occurred under light irradiation and that the extentof conversion and the molecular weight of the produced polymer with thetime (J. Polym sci; part A; polym. chem., 32, 2911 (1994)). According tothese methods, it is possible to control the molecular weight in aconsiderably wide range. However, these methods lack universalitybecause they require a special polymerization initiator or a use oflimited kinds of monomer.

[0006] In anionic polymerization, a precise control of the molecularweight is possible by a polymerization on method called livingpolymerization. Recently, it has also become popular to research apolymerization system which enables living polymerization in radicalpolymerization For example, it has been shown in Japanese PatentPublication No. 94-199916 A that, by using a radical polymerizationinitiator such as benzoyl peroxide together wait a stable free radicalagent such as 2,2,6,6-tetramethyl-piperidinyloxy (TEMPO), a living-likepolymerization of styrene can be achieved. According to this method, byselecting a polymerization condition, the molecular weight of thepolymer obtained will depend not only on the polymerization temperaturebut also on the amounts of the initiator and the stable free radicalagent used, so that one can control the molecular weight by thoseamounts to a certain extent.

[0007] Thus, when the above method is used, one can obtain a resinhaving a controlled molecular weight. However, this method has adrawback that the reaction rate in this method is so slow that it takesconsiderably more time compared with the usual radical polymerization toreach a high extent of conversion. In addition, coloration of theobtained polymer may sometimes occur depending on few reactioncondition. Furthermore, TEMPO requires special attention in its handlingand storage because it exists in radical state, and it is also veryexpensive. This method has thus some shortcomings that for example, itrequires more production costs compared with conventional methods.

[0008] In view of such a situation, the present inventors haveconcentrated their efforts on controlling the radical reaction of vinylmonomer with the aim of increasing productivity and improving practicalphysical properties of radically polymerized vinyl polymers. In result,we have found by chance a method for obtaining a vinyl polymer having ahigh molecular weight and a restrained molecular weight distributionwhile retaining a high polymerization rate by including a specificsubstituted alkylhydroxylamine in the polymerization system, and thuscompleted the present invention.

SUMMARY OF THE INVENTION

[0009] The present invention provides a process for producing a vinylpolymer characterized in that, in a radical polymerization of a vinylmonomer, a substituted hydroxylamine represented by a general formula:

(in which R₁ and R₂ represent hydrogen, a (substituted) aliphatichydrocarbon group having one or more carbon atom(s) or an aromatichydrocarbon group) and/or a general formula.

[0010] (in which and R₃ and R₄ represent a (substituted) aliphatichydrocarbon group having one or more carbon atom(s)) is added.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention is described below in more detail

[0012] In each of R₁ and R₂ of the general formula (I) of the presentinvention, the aliphatic hydrocarbon group may include, for example,methyl, ethyl, isopropyl, t-butyl, butyl and the like group, and thearomatic hydrocarbon group may include, for example, phenyl, bensyl andthe like group.

[0013] Similarly, —R₃—R₄ in the general formula (2) may include adivalent (substituted) aliphatic hydrocarbon group corresponding tothose groups in the general formula (1) such as —CH₃CH₂—,—CH₂CH₂CH₂CH₂—, —CH(CH₂)CH₂—CH(CH₂)CH₂——C(CH₂)₂CH₂—C(CH₂)₃CH₂—,—CH₂CH₂CH₂CH₂—CH₂CH₂CH₂CH₂—, or the like.

[0014] Furthermore, the hydrocarbon groups i the above general formulas(1) and (2) may optionally be substituted, and the substitutent mayinclude, for example, an aliphatic hydrocarbon such as a methyl or ethylgroup, an aromatic hydrocarbon such as a phenyl group, halogen ahalogenated hydrocarbon, a carbonyl group, a hydroxy group, an aminogroup, and the like.

[0015] In the present invention, the substance presented by the generalformula (1) (substituted hydroxylamine) may includedimethylhydroxylamine, dimethylhydroxylamine, isopropylhydroxylamine,dimethylhydroxylamine, and the like.

[0016] In the present invention, the substance represented by thegeneral formula (2) may include N-hydroxylamine N-hydroxylsuccinimide,N-hydroxylphthalimide and the like.

[0017] In the present invention, although the radical polymerization maybe initiated by any of the known methods, for example, using aninitiator, heat, light or radioactive rays, it is preferable to use aninitiator. Although there is no special restriction on the ratio of thesubstance represented by the above general formulas(1) and (2)(substituted hydroxylamine) used to the radical polymerizationinitiator, it is preferable to use a mole ratio between the substancerepresented by the above general formulas(1) and (2) and the radicalpolymerization initiator at 0.01/1-100/1 (substance represented by theabove general formulas(l) and (2)[substituted hydroxylamine]/radicalpolymerization initiator), more preferably at 0.1/1-10/1, andparticularly preferably at 0.1/1-1.0/1. At a mole ratio of the substancerepresented by the above general formula (1) and (2) to the radicalpolymerization initiator below 0.01/1, it will be difficult to controlthe molecular weight and molecular weight distribution, while at a moleratio above 100/1, he polymerization rate will decrease.

[0018] There is no special restriction on the vinyl monomer used in thepresent invention, and it may be exemplified by aromatic vinylcompounds, α, β-unsaturated carboxylic acids, α, β-unsaturatedcarboxylic acid esters, α, β-unsaturated carboxylic amides, α,β-unsaturated nitrites, vinyl carboxylates, vinyl halides, vinylidenehalides, conjugated dienes and the like compounds capable of radicallypolymer.

[0019] As an aromatic vinyl compound, although styrene is typicallyused, other aromatic vinyl compounds, for example, an alkyl-substitutedstyrene such as o-methylstyrene, p-methylstyrene, m-methylstyrene,2,4-dimethylstyrene, p-ethylstyrene, p-t-butylstyrene, α-methylstyreneor α-methyl-methylstyrene, and an halogenated styrene such aso-chlorostyrene or p-chlorostyrene may also be used. A preferablearomatic vinyl compound includes, for example, styrene, α-methylstyreneand p-methylstyrene; and styrene is especially preferable.

[0020] The α-unsaturated carboxylic acid may include acrylic acid,methacrylic acid and the like. The α, β-unsaturated carboxylic acidester may include, for example, alkyl acrylates such as methyl acrylate,ethyl acrylate and n-butyl acrylate, alkyl methacrylates such as methylmethecrylate, ethyl methacrylate and butyl methacrylate, and derivativesthereof. The α,β-unsaturated carboxylic amide may include, for example,acrylamide, methacrylamide, and derivatives thereof. The α,β-unsaturated nitrile may include acrylonitrile, methacrylonitrile,α-chloroacrylonitrile and the like. The vinyl carboxylates may includevinyl acetate, vinyl propionate and the like. The vinyl halide mayinclude vinyl fluoride, vinyl chloride, vinyl bromide, vinyl iodide andthe like. The vinylidene halide may include vinylidene fluoride,vinylidene chloride, vinylidene bromide, vinylidene iodide and the like.The conjugated diene compound may include butadiene, isoprene,chloroprene, piperidene, chlorobutadiene and the like.

[0021] There is no special restriction on the radical polymerizationinitiator used in the present invention so far as it is capable ofinitiating radical polymerization, and the following compounds may beused, for example: organic peroxides, for example, peroxyketals such as2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,1,1-bis(t-butylperoxy)cyclohexane andn-butyl-4,4bis(t-butylperoxy)valerate, hydroperoxides such as cumenehydroperoxide and diisopropylbenzene peroxide peroxide, dialkylhydroperoxides such as t-butylcumyl peroxide and di-t-butyl peroxide,diacyl peroxides such as lauroyl peroxide and benzoyl peroxide,peroxydicarbonates such as bis(t-butylcyclohexyl) peroxydicarbonate, andperoxyesters such as t-butyl peroxybenzoate, t-butyl peroxyacetate and2,5-dimethyl-2,5-dibenzoylperoxy)hexane; azo compounds such asazoisobutyronitrile, 2,2-iazobis(2methylbutyronitrile), and1,1-azobis(cyclohexaril-carbonitrile); and peroxide such as benzoylperoxide.

[0022] The radical polymerization initiator is preferably used at a moleratio to vinyl monomer of 0.001/100-10/100 (radical polymerizationinitiator/vinyl monomer), and more preferably at a mole ratio of0.01/100-1/100. This is because, at a ratio of radical imitator to vinylmonomer below 0.001/100, it will be difficult to control the molecularweight, and at a mole ratio above 10/100, the polymerization willproceed so quickly that it becomes difficult to control the reaction.

[0023] There is no special restriction on the process of carrying outthe polymerization of the present invention, and any of the usualpolymerization modes such as bulk polymerization, suspensionpolymerization, bulk-suspension polymerization and solutionpolymerization may be used In the case of solution polymerization, nomore than 20 parts by weight of solvent may be included in the processwith 100 parts by weight of vinyl monomer, if necessary. Solvent morethan 20 parts by weight is disadvantageous because it will decrease thepolymerization rate and productivity.

[0024] There is no special restriction on the solvent included in teeprocess so far as the monomer and the produced polymer as soluble in thesolvent. An example of solvent may be toluene, ethylbenzene, methylethyl ketone, benzene or the like, and toluene or ethylbenzene isespecially preferred because the boiling points are close to thepolymerization temperature. The above solvents may be used alone or incombination.

[0025] Furthermore, according to the process of the present invention,the molecular weight can be controlled by the amounts of the initiatorand the monomer as well as the extent of conversion, so that thepolymerization can be conducted in a very simple mode. Furthermore,according to the process of the present invention the molecular weightcan be controlled by the amounts of the initiator and substancerepresented by the above general form (1) or (2). It is, therefore, veryeasy to industrialize the present invention. The process according tothe present invention may be carried out in a continuous mode or inbatch.

[0026] The polymerization temperature at which the present inventionoperates is typically 60° C.-160° C., and preferably 90° C.-150° C. At atemperature below 60° C., the reaction rate will be too low for anindustrial production process, while at a temperature above 160° C. sidereactions during the polymerization will occur to a extent notnegligible, rendering the reaction control difficult.

[0027] When a stricter control is required in carrying out the presentinvention, a compound which has a function controlling heatpolymerization may be used, if necessary. Among the compounds havingsuch a function are, for example, phenylphosphonic acid, D,L-camphor-10-sulfonic acid, p-toluenesulfonic acid,2-fluoro-1-methylpyridininium and the like.

[0028] When a thermoplastic resin is produced by the process of thepresent invention, admixes, stabilizers or the like agents usually usedmay be added. For example, in the case of styrene-based thermoplasticresins, a lubricant such as mineral oil, silicone oil, zinc stearate,calcium stearate, or ethylenebisstearylamide, an oxidation inhibitorsuch as a phenolic or phosphorus antioxidant, a UV absorbent, and acolorant may be added during or after the polymerization.

[0029] The present invention will be further illustrated by thefollowing Examples to which the present invention is not restricted.

EXAMPLES

[0030] As described below, the polymers of Examples 1-7 and References1-2 were subjected to the follow measurements (1) and (2), and theresults are summarized in Table 1.

[0031] (1) Measurement of conversion

[0032] The extent of conversion was calculated bygas-chromatographically quantifying the amount of remaining monomer inthe reaction solution sampled at a given interval during the reaction.

[0033] (2) Measurement of the molecular weight

[0034] For the polymer in the reaction solution sampled at a giveninterval during the reaction, the molecular weight was measuredaccording to a GPC method using a GPC (LC-10A) manufactured by SHIMADZUCORPORATION and GPC columns (three KF-806L columns in tandem)manufactured by Showa Denko K.K.

[0035] Unless otherwise indicated, the polymerization reaction wasearned out under nitrogen stern in a polymerization apparatus in which areactor having 20 L inner volume equipped with an agitator was connectedto a biaxial extender equipped with a vent line. The stat time of thereaction was defined as the point when the temperature reached 95° C.

EXAMPLE 1

[0036] A stock solution consisting of 150 mol of styrene, 0.3 mol ofbenzoyl peroxide and 0.15 mol of dimethylhydroxylamine was introducedinto the reaction, and heated with stirring at 95° C. for 3.5 hours.After raising the temperature to 130° C., stirring was continued foradditional 4.5 hours to synthesize the polymer. After removing remainingmonomer polystyrene was recovered from the biaxial eider to obtain thepolymer of Example 1.

EXAMPLE 2

[0037] A stock solution consisting of 150 mol of styrene, 0.3 mol ofbenzyl peroxide and 0.09 mol of diethylhydroxylamine was introduced intothe reactor, and polymerized at 95° C. for 3 hours. Then, the polymer ofExample 2 was obtained by following the same procedures as those inExample 1.

EXAMPLE 3

[0038] A stock solution consisting of 150 mol of styrene, 0.3 mol ofbenzoyl peroxide and 0.21 mol of diethylhydroxylamine was introducedinto the reactor, and the polymer of Example 3 was then obtained byfollowing the same procedures as those in Example 1.

EXAMPLE 4

[0039] A stock solution consisting of 150 mol of styrene, 0.3 mol ofbenzoyl peroxide, 0.15 mol of diethylhydroxylamine and 0.3 mol ofcamphorsulfonic acid was introduced into the reactor, and the polymer ofExample 4. Was obtained by following the same procedures as those inExample 1.

EXAMPLE 5

[0040] A stock solution consisting of 150 mol of styrene, 0.3 mol ofbenzoyl peroxide and 0.15 mol of diethylhydroxylamine was introducedinto the rector, and polymerized at 130° C. for 6 hours. Then, thepolymer of Example 5 was obtained by following the same procedures asthose in Example 1.

EXAMPLE 6

[0041] A stock solution consisting of 150 mol of styrene, 0.15 mol ofbenzoyl peroxide and 0.075 mol of diethylhydroxylamine was introducedinto the reactor, and the polymer of Example 6 was the obtained byfollowing the same procedures as those in Example 1.

EXAMPLE 7

[0042] A stock solution consisting of 150 mol of styrene, 0.15 mol ofbenzoyl peroxide and 0.075 mol of diethylhydroxylamine was introducedinto the reactor, and the polymer of Example 6 was then obtained byfollowing the same procedures as those in Example 1.

Reference 1

[0043] The polymer of Reference 1 was obtained by following the sameprocedures as those in Example 1 with the exceptions that a stocksolution consisting of 150 mol of styrene and 0.3 mol of benzoylperoxide was introduced into the reactor and that the reaction wasstopped a 2 hours at 130° C.

Reference 2

[0044] The polymer of Reference 2 was obtained by following sameprocedures as those in Example 1 with the exceptions that a stocksolution consisting of 150 mol of styrene, 0.3 mol of benzoyl peroxideand 0.36 mol of 2,2,6,6tetraethyl-1-piperidinyloxy was introduced intothe reactor and that the polymerization time was 80 hours.

EFFECTS OF THE INVENTION

[0045] As described above, a radically polymerized vinyl polymer havinga high molecular weight and a controlled molecular weight distributioncan be obtained by the process of the present invention, even under apolymerization condition at a high temperature. The present inventionprovides, therefore, a process enabling to produce vinyl polymers whichpromise to have practical properties such as appearance, mechanicalproperties and heat resistance useful as materials for various moldingsand coatings. Thus, the industrial and technical value of the presentinvention is extremely high. TABLE 1 Reaction Con- Time version Example(h) (%) Mn × 10⁻⁴ Mw × 10⁻⁴ Mw/Mn Example 1 2 21.0 4.06 6.62 1.53 4 40.45.34 7.58 1.36 8 74.6 7.80 10.45 1.30 Example 2 1 31.2 3.36 5.21 1.52 254.6 4.23 6.55 1.55 3 70.2 5.33 8.04 1.51 Example 3 2 11.7 4.87 7.891.62 4 18.2 5.86 9.02 1.54 6 42.5 7.08 10.55 1.49 8 80.3 8.81 12.51 1.42Example 4 2 31.6 4.13 7.31 1.77 4 68.1 5.69 9.39 1.65 8 87.9 6.74 9.771.45 Example 5 1 12.4 2.40 4.82 2.01 3 45.3 5.22 8.87 1.70 6 88.6 7.6812.60 1.64 Example 6 2 18.5 6.21 10.43 1.68 4 42.7 12.77 19.66 1.54 879.9 17.20 29.58 1.42 Example 7 2 10.1 5.61 10.22 1.82 4 20.4 8.94 15.651.75 8 55.7 15.26 26.09 1.71 Reference 1 0.5 54.3 4.75 15.44 3.25 1 70.24.44 13.01 2.93 2 89.4 5.26 13.26 2.52 Reference 2 20 22.1 0.22 10.501.33 40 43.6 0.51 9.77 1.28 80 70.5 0.80 11.30 1.27

1. A process for producing a vinyl polymer characterized in that, in aradical polymerization of a vinyl monomer, a substituted hydroxylaminerepresented by a general formula:

(in which R₁ and R₂ represent hydrogen, a (substituted) aliphatichydrocarbon group having one or more carbon atom(s) or an aromatichydrocarbon group) and/or a general formula:

(in which R₃ and R₄ represent a (substituted) aliphatic hydrocarbongroup having one or more carbon atom(s)) is added.
 2. A process forproducing a vinyl polymer set forth in claim 1 characterized in that theradical polymerization is carried out a radical polymerizationinitiator.
 3. A process for producing a vinyl polymer set forth in claim2 characterized in that the radical polymer initiator is used at a moleratio between said radical polymerization initiator and the vinylmonomer of 0.001/100-101100 (radical polymerization initiator/vinylmonomer).
 4. A process for producing a vinyl polymer set forth in claim2 or 3 characterized in that the substituted hydroxylamine set forth inclaim 1 and the radical polymerization initiator are used at a moleratio between said substituted hydroxylamine and said radicalpolymerization initiator of 0.01/1-100/1 (substitutedhydroxylamine/radical polymerization initiator).
 5. A process forproducing a vinyl polymer set forth in any one of claims 1-4characterized that the vinyl monomer is an aromatic compound.